Antimatter-Hunting Experiment Ready for Space Mission

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A cutting-edge experiment hunting for antimatter galaxies and
signs of dark matter that was very nearly cancelled is finally
poised to voyage into orbit aboard the next-to-last space shuttle
mission.

The ambitious
Alpha Magnetic Spectrometer is a more than 15,000-pound
(6,900-kilogram) device searching for cosmic- rays — high-energy
charged particles from outer space. The nearly $2 billion
experiment will ride up to the International Space Station on the
shuttle Endeavour on Friday (April 29).

The instrument will employ a nearly 4,200-pound (1,900 kg)
permanent magnet to generate a strong, uniform magnetic field
more than 3,000 times more intense than Earth's. This deflects
cosmic rays so that a battery of detectors can analyze their
properties, such as charge and velocity, and beam their findings
to Earth. [ Video:
Sifting Through the Cosmic Sand for Dark Matter ]

But while the Alpha Magnetic Spectrometer promises big
discoveries for the field of astrophysics, just getting the
instrument on the launch pad has been a challenge.

After the 2003 Columbia shuttle accident, NASA initially
cancelled the mission that would deliver the spectrometer to the
space station. The mission was reinstated after substantial
lobbying from lawmakers and scientists. Last year, engineers
replaced the big magnet on the spectrometer with a longer-lasting
one to get more science out of the instrument through 2020, the
expected end life of the space station. [ Photos:
Shuttle Endeavour's Last Mission ]

"It took 17 years and 600 physicists from 16 countries to get
this far — it's been a major international effort," Nobel
laureate
Samuel Ting, principal investigator for the Alpha Magnetic
Spectrometer,told SPACE.com. "We've checked and rechecked
everything to make sure it's right. Now we're just waiting to
launch it."

Cosmic rays can pack up to millions of times more energy than any
manmade particle accelerator is capable of. As such, they can
reveal details about the universe that no experiment on Earth
could. By analyzing cosmic rays, researchers hope the Alpha
Magnetic Spectrometer could help solve a number of science's most
baffling mysteries, such as whether
antimatter galaxies exist and what dark matter is made of.

One of the most perplexing questions in physics is why matter
seems to dominate the known cosmos when it should be made of
equal parts matter and its mirror image antimatter, and it may be
that antimatter does exist in vast amounts in the universe. If
the Alpha Magnetic Spectrometer detects anti-helium or heavier
antimatter elements, that could be strong proof of antimatter
galaxies, as such large bits of antimatter could likely only be
made by antimatter stars.

Another enigma is the nature of unseen, as-yet-unidentified
dark matter makes up about 85 percent of all matter in the
universe, which scientists know exists because of the
gravitational effects it has on galaxies. One of the leading
candidates for dark matter is a particle known as the neutralino.
If neutralinos exist, when they collide with each other, they
should give off a large number of high-energy anti-electrons that
the Alpha Magnetic Spectrometer can detect.

Besides exploring known mysteries in science, "this is the first
time we will study cosmic rays in space over a long duration with
very high accuracy, so we're entering a new area where we really
do not know what we will find," Ting said.

"In space, there are two types of particles. One has no charge,
namely light rays and neutrinos, and traditionally, over the last
century, all our understanding about space has been based on
study of these from many, many telescopes in space and on the
ground," Ting said. "When it comes to charged particles such as
cosmic rays, "because they carry a charge, they must have mass,
and because they have mass, they get absorbed in Earth's
atmosphere, so you therefore have to got to space to look at
them."

Investigating the electrical charge on charged particles requires
a magnet. Originally the Alpha Magnetic Spectrometer was going to
fly with a superconducting magnet that would last for three years
until the liquid helium needed to keep it cool ran out.

"When we tested the superconducting magnet in a thermal vacuum
chamber to simulate space, we found it could only be operated for
three years before it needed to get its liquid helium refilled,
and there's really no way to do so without the space shuttle,
which has been terminated," Ting explained.

Rather than have the Alpha Magnetic Spectrometer operate with a
superconducting magnet for only three years "and become a museum
piece," Ting said, they
decided to go with a permanent magnet that actually flew on a
1998 shuttle flight.

Although the permanent magnet is weaker than the superconducting
one — essentially making it 30 percent less sensitive — President
Barack Obama extended the life of the International Space Station
through at least 2020 instead of shutting it down about 2015,
effectively granting the experiment six times as much time to
collect data, "so you have a tremendous net gain," Ting
explained.

In fact, NASA originally cancelled the shuttle mission to deliver
the device to the International Space Station following the 2003
Columbia shuttle disaster. Congress later approved funding for
its flight upward.

"Many leading scientists and major political leaders in the
Senate and House spoke up for the Alpha Magnetic Spectrometer,"
Ting said. "The idea is that if building the International Space
Station cost $100 billion, there should really be a good science
project there."

Follow SPACE.com contributor Charles Q. Choi on Twitter
@cqchoi. Visit SPACE.com
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